1. Field of the Invention
The present invention relates to an electroconductive paste and a method of producing the same and, in particular, to an electroconductive paste for forming internal electrodes in a laminated ceramic electronic part such as a laminated ceramic capacitor or the like.
2. Description of the Related Art
In recent years, the size of electronic devices have been decreased. Thus, a reduction in size of the electronic parts has needed to also rapidly progress. Correspondingly, a reduction of the thickness of ceramic layers has been also required in the field of laminated ceramic electronic parts, requiring a reduction in the thickness of the green sheets which are fired during formation of ceramic layers. Moreover, the capacity of capacitors in the field of laminated ceramic capacitors has increased. Thus, there has been intensive demand for reduction in thickness of ceramic green sheets.
Ordinarily, an electroconductive paste for forming internal electrodes is printed onto ceramic green sheets by screen printing in production of laminated ceramic electronic parts such as laminated ceramic capacitors or the like. Then the ceramic green sheets are laminated, and the ceramic laminate is fired.
The ceramic green sheets are formed by forming ceramic slurry into a sheet by the doctor blade method or the like. The ceramic slurry is formed by mixing a binder resin and an organic solvent are mixed with ceramic raw material powder. Thus, a ceramic green sheet is formed. The electroconductive paste is produced by dispersing an electroconductive powder in an organic vehicle containing a binder resin and a solvent.
However, so-called sheet-attack problems occur during production of laminated ceramic electronic parts. In particular, the solvent contained in the electroconductive paste dissolves the binder resin contained in the ceramic green sheet, so that the ceramic green sheet swells and is dissolved. This “sheet-attack” defect exerts an severe influence over the formation of thin layers of the ceramic green sheets.
Therefore, it has been proposed that hydrogenated terpineol acetate be used as a solvent in the electroconductive paste (see Japanese Unexamined Patent Application Publication No. 7-21833 (Patent Document 1)).
However, a further reduction in layer-thickness of ceramic green sheets has been required in recent years. Even if the electroconductive paste as described in Patent Document 1 is used, the “sheet-attack” problem can not be sufficiently prevented, and laminated ceramic electronic parts formed by use of the ceramic green sheets are distorted or cracked.